143 Fig. 1 shows the bone and muscle structure of a person's arm supporting a 5.0 kg mass in 5.0kg mase 5.0hg 20N 20N 5.0 om - O cin 15cm 15 em 35 cm 35 gm Fig 2 Fig 1 equilibrium. The forearm is horizontal and is at right angles to the upper arm. Fig. 2 shows the equivalent mechanical system. FM is the force exerted by the biceps muscle and F, is the torce at the elbow joint. The perpendicular distance between the lines of action of FM and F, is 5.0 cm. (a) (i) Explain why the 20N force has been included. (ii) State the conditions which must be met by the forces when the arm is in equilibrium. (b) (i) Calculate the magnitude of the force FM. (ii) Show that FAM has the same magni- tude when the forearm is at 45 to the horizontal with the upper arm still vertical. (c) In many athietes the distanue between the elbow joint, E, and the muscle attach- ment, P, is greater than 5.0 cm. Explain how this is an advantage in lifting and throwing events. [AEB, '89]

143 Fig. 1 shows the bone and muscle structure of a person's arm supporting a 5.0 kg mass in 5.0kg mase 5.0hg 20N 20N 5.0 om - O cin 15cm 15 em 35 cm 35 gm Fig 2 Fig 1 equilibrium. The forearm is horizontal and is at right angles to the upper arm. Fig. 2 shows the equivalent mechanical system. FM is the force exerted by the biceps muscle and F, is the torce at the elbow joint. The perpendicular distance between the lines of action of FM and F, is 5.0 cm. (a) (i) Explain why the 20N force has been included. (ii) State the conditions which must be met by the forces when the arm is in equilibrium. (b) (i) Calculate the magnitude of the force FM. (ii) Show that FAM has the same magni- tude when the forearm is at 45 to the horizontal with the upper arm still vertical. (c) In many athietes the distanue between the elbow joint, E, and the muscle attach- ment, P, is greater than 5.0 cm. Explain how this is an advantage in lifting and throwing events. [AEB, '89]

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter8: Rotational Equilibrium And Dynamics

Section: Chapter Questions

Problem 91AP: The Iron Cross When a gymnast weighing 750 N executes the iron cross as in Figure lN.91a, the...

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